Sprouted vegetable seeds sterilizing method, and sprouted vegetables cultivating method

Abstract: An effective method for sterilizing seeds for sprouted vegetables and a sprouted vegetables cultivating method in which the growth of sprouted vegetables is promoted, with restraining the occurrence of their putrefaction caused by the breeding of microorganisms, are provided. Seeds for sprouted vegetables are subjected to a sterilizing treatment comprising exposing seeds to a high temperature of 70 °C or more and then quenching the seeds quickly. By making shorter the time of exposure even to a high temperature, this is 70 °C or more, it is possible to obtain seeds in which their putrefaction due to the breeding of microorganisms which has hitherto occurred in the growing course of sprouted vegetables can be remarkably reduced, without giving any bad influence upon the sprouting and growth of sprouted vegetables at all. Furthermore, the present invention provides a method for cultivating sprouted vegetables by use of seeds which have been exposed to a high temperature of 70 °C or more and then quenched quickly. By use of such seeds subjected to the high-temperature sterilizing treatment, it is possible to rear sprouted vegetables with a smaller quantity of their putrefaction after soaking, and to harvest sprouted vegetables capable of being preserved for a long period of time.

Description: The present Invention relates to a method for sterilizing seeds for sprouted vegetables, for example seeds for various kinds of sprouts such as black mung bean sprouts, mung bean sprouts, soybean sprouts or alfalfa sprouts, and KAIWARE radish or the likes, and a method for cultivating sprouted vegetables. As a problem of the so-called sprouted vegetables, i.e. various kinds of sprouts, which will be good to eat after their seeds are sprouted and somewhat grown up, it is important how to promote their rearing. Although sprouted vegetables will be cultivated at a temperature and humidity suitable for their sprouting and growth, such a rearing environment is also an environment suitable for the breeding of various kinds of microorganisms. Seeds are generally contaminated on the outer surface of their shells and sometime on the inner surface thereof by microorganisms, and this contamination becomes a factor for putrefying sprouted vegetables in their cultivation. In particular, in a case of sprouts, seeds must be sprouted and grown up in a high temperature and high humidity environment while supplying water thereto at all times, and under such a situation, it is therefore very difficult to restrain the breeding of microorganisms. In a case where sprouted vegetables are cultivated in the prior art, seeds are washed with water so as to remove microorganisms therefrom or subjected to a sterilizing treatment using chlorine or other chemicals, before their soaking which comprises dipping seeds in warm water for the purpose of promoting their sprouting. However, it is difficult to destroy microorganisms effectively, without damaging the life activity performing abilities of seeds as a living thing, i.e. their sprouting and growing abilities, and in addition, it is not permitted to use strong chemicals because sprouted vegetables are foods which are often eaten fresh. In the prior art, accordingly, microorganisms are inevitably permitted to breed in some extent when sprouted vegetables are reared, and as a result, it is unavoidable that the putrefaction of sprouted vegetables is caused by microorganisms in the course of their rearing and the preservation of sprouted vegetables after their harvest is worsened. Methods of decontaminating and sterilizing vegetable seeds through prolonged application of heat are disclosed in SU-A-422368 and in FR-A-1260436. state of things. The present invention is intended to provide an effective method for sterilizing seeds for sprouted vegetables, for the purpose of supplying seeds which can be grown to sprouted vegetables, with no trouble caused by the breeding of microorganisms. In particular, it is an object of the present invention to provide a method for sterilizing seeds for sprouted vegetables, which can effectively destroy microorganisms, without using any chemicals, and which can further supply seeds capable of being preserved for a long period of time after their sterilizing treatment. Furthermore, it is an object of the present invention to provide a novel method for cultivating sprouted vegetables, which can promote the rearing of sprouted vegetables, with restraining the occurrence of their putrefaction due to the breeding of microorganisms. For the purpose of solving the aforementioned problems in the sterilizing treatment of seeds for sprouted vegetables, according to the present invention, there is adopted a sprouted vegetable seeds sterilizing method comprising bringing seeds into contact with a high temperature of about 70°C to about 90°C for a time of a about 10 to about 30 seconds, said contact being effective for pasteurizing microorganisms existing on the surface of seeds, and sometime in the inside thereof after being invaded from the external wounds or broken portions of seeds, without damaging the life functions of seeds' embryos, with accuracy and only for a proper period of time, and then quenching the seeds quickly to ambient temperature. As for the said temperature to which seeds for sprouted vegetables are to be exposed and time of exposure to that temperature in the present invention, optimum values will be concretely selected depending upon an object of sprouted vegetable seeds. In order to expose seeds for sprouted vegetables to such a high temperature, they may be dipped in hot water having a predetermined temperature, or exposed to steam. When it is not required to give humidity to seeds, dry heat such as heated air or combustion gas may be used. In addition, as to the said temperature and time of exposure, values to be selected will vary depending on whether a high temperature is given by dry heat such as heated air or by wet heat such as hot water or steam. After the heating treatment, the sprouted vegetable seeds are quickly quenched, in order that any obstacle due to heat is not left in the seeds. For the same purpose, it is also effective to subjecting seeds to a preheating treatment before they are exposed to a predetermined high temperature. In the sprouted vegetable seeds sterilizing method, seeds for sprouted vegetables are exposed to a high remperature for a short period of time and then quenched quickly, as mentioned above, whereby they can be effectively sterilized, without damaging the function of seeds as a living thing. And, in a case where the heat to which seeds are to be exposed is dry heat such as heated air, seeds are quenched quickly by cold air or the like after the heating treatment, and the seeds get into a condition suitable for preservation as sterilized. These seeds under preservation will be directly taken out and they can be used as sprouted vegetable seeds which can be cultivated, without causing any putrefaction of them by the breeding of microorganisms. In order to achieve the aforementioned purpose on the cultivation of sprouted vegetables, furthermore, according to the present invention, there is adopted a method comprising cultivating seeds for sprouted vegetables, after they are subjected to a sterilizing treatment as specified above. The manner of exposing seeds to a high temperature is the same as mentioned above. In the sprouted vegetables cultivating method according to the present invention, sprouted vegetable seeds are sterilized as mentioned above, whereby microorganisms which become an obstacle for rearing sprouted vegetables can be remarkably destroyed and therefore, the putrefaction of sprouts due to the breeding of microorganisms during their rearing can be extremely reduced. Since sprouted vegetables reared by the cultivating method according to the present invention get into a condition that microorganisms breed less, moreover, it is possible, according to the present invention, to harvest sprouted vegetables capable of being preserved for a long period of time. Since seeds subjected to a sterilizing treatment at a high temperature are used for cultivation by the sprouted vegetables cultivating method according to the present invention, furthermore, a further sterilizing treatment using chlorine or the like applied to sprouted vegetables in the course of their cultivation, for example in the soaking or intermediate sterilizing treatment, acts effectively upon microorganisms which are weakened, but live still, whereby the putrefaction of sprouted vegetables can be remarkably reduced. The sprouted vegetable seeds sterilizing method and the sprouted vegetables cultivating method according to the present invention will be concretely described in accordance with their preferred embodiments. As for the said temperature and time of exposure to that temperature, optimum values will be concretely selected depending upon an object of seeds. As a medium by which seeds are exposed to such high temperature, there can be used wet heat such as heated water or steam or dry heat such as heated air or heated gas. In a case where seeds for sprouted vegetables are subjected to a sterilizing treatment by dry heat and quenched quickly by cold air or the like, the seeds can be preserved as sterilized and they can be immediately used for cultivation because their humidity is not increased after such treatment and they are not deteriorated or putrefied during the preservation. In the sterilizing treatment according to the present invention, in general, the higher the temperature to which sprouted vegetable seeds are to be exposed is, the shorter the time of exposure becomes. However, the manner for giving heat to sprouted vegetable seeds will depend upon whether wet heat or dry heat is used, and the temperature and time which have no bad influence upon the life of sprouted vegetable seeds as a living thing will also vary as mentioned above. Combinations of the temperature and time which are applicable to the high-temperature sterilizing treatment of seeds for sprouted vegetables, according to the present invention, will be generally exemplified for a standard as follows. 90 °C about 10 seconds 80 °C 10 ∼ 20 seconds 70 °C 20 ∼ 30 seconds Since the selected temperature and time must be accurate because the object is a living thing, seeds are accurately exposed to a predetermined temperature for a given period of time. It is therefore important to put the seeds into a water tank kept at ambient temperature after that heating so that they are quickly quenched nearly to ambient temperature, and also to preheat them below to 45°C as occasion demands. Furthermore, it is important to expose seeds to a predetermined temperature uniformly as they are stirred during the heating sterilization. In short, it is the point to effectively destroy microorganisms on the outer surface of seed shells or on the injured or broken portions thereof, without damaging the life function of seed embryos. In the next place, the sprouted vegetables cultivating method according to the present invention will be concretely described in accordance with its preferred embodiment. In a case where seeds are sprouted and grown up, thereby making sprouted vegetables, the seeds are usually subjected to the so-called soaking which comprises dipping them in warm water having a temperature of about 30 ∼ 40 °C. The present invention comprises, before the aforementioned soaking step, carrying out a sterilizing treatment. Then, the seeds which have been subjected to the sterilizing treatment as mentioned above will be cultivated after they are passed through the same soaking step as in the prior art. In the soaking or intermediate sterilizing treatment carried out in the course of their cultivation, a further sterilizing treatment using chlorine or the like is carried out. The effect of said further sterilizing treatment applied in the course of their cultivation will be remarkably revealed in the sprouted vegetables cultivating method according to the present invention. That reason will be understood to be that the said further sterilizing treatment using clorine or the like acts effectively upon microorganisms which are weakened, but not destroyed by the high-temperature treatment. In addition, when seeds are heated by hot water or steam, they are given humidity and therefore the soaking time will vary. The test results in a case where the method according to the present invention which comprises exposing seeds to a high temperature for a short period of time and rearing the seeds has been applied to the cultivation of mung bean sprouts, is given by way of example in Table 1. In Table 1, Sample Nos. 3 and 4 represent, for comparison, the data obtained on the seeds which have not been subjected to the high-temperature sterilizing treatment according to the present invention. Sample Nos. 1 and 2 represent the results obtained on the seeds which have been subjected to the high-temperature sterilizing treatment according to the present invention, which comprises dipping seeds in hot water having a temperature of 70 °C - 90 °C for a short period of time, and then dipped in normal temperature water so as to be cooled. These seeds have been the same kind of seeds subjected to the same specific gravity selection, and they have been reared under the quite same cultivating condition and within the same cultivation room, as represented in Table 1. Sample No. 1 2 3 4 Pretreatment Specific Gravity Selection Sterilizing Treatment Dipping Sterilization in Hot Water for Short Time not treated not treated Temperature of Soaking Water 23°C 23°C 23°C 23°C Quantity of Occured Putrefaction (per 500kg of Harvest) 0.01 kg 0.3 kg 12.3 kg 11.3 kg In a case where the seeds were reared after subjected to the high-temperature treatment according to the present invention, as described above, the quantity of putrefied sprouts could be decreased to below several tenth parts as compared with the prior art. Also in the result of the preservation test, the remarkable result could be obtained in the present invention. By virtue of the method according to the present invention, it is possible to obtain seeds whose putrefaction can be effectively prevented in the rearing of sprouted vegetables. In a case where dry heat such as heated air or combustion gas is used as a high temperature to which seeds are to be exposed, moreover, according to the sprouted vegetable seeds sterilizing method of the present invention, it is possible to preserve seeds as sterilized and to cultivate the seeds as they are, with no fear of deteriorating or putrefying the seeds during the preservation, because their humidity is not increased as in a case where they are treated by wet heat such as hot water. According to the sprouted vegetables cultivating method of the present invention it is possible to rear sprouted vegetables, with their putrefaction remarkably reduced, under such a condition that microorganisms breed extremely less. It is also possible to obtain sprouted vegetables capable of being preserved for a long period of time, because seeds can be cultivated under such a condition that microorganisms breed less, thereby obtaining sprouted vegetables on which microorganisms are less deposited. Accordingly, it is possible to remarkably reduce the breeding of microorganisms because various sterilizing treatments subjected to seeds in the course of their cultivation act effectively upon microorganisms which are weakened by the high-temperature treatment subjected to the seeds.

Claims: A method of sterilizing seeds for sprouts, which comprises exposing said seeds to a temperature in the range of about 70°C to about 90°C for a time of about 10 to about 30 seconds, wherein shorter duration is used with higher temperature; and then quenching said seeds to ambient temperature. The method of claim 1, wherein said temperature in the range of about 70°C to about 90°C is effected by dry heat. The method of claim 2, wherein said dry heat is effected by heated air or combustion exhaust gases. The method of claim 1, wherein said temperature of about 70°C to about 90°C is effected by wet heat. The method of claim 4, wherein said wet heat is effected by hot water. The method of any of claims 1 to 4, wherein said seeds are preheated up to about 45°C prior to exposing said seeds to a temperature in the range of about 70°C to about 90°C. The method of any of claims 1 to 6, wherein said quenching is effected by bringing said seeds into contact with air at ambient temperature. The method of any of claims 1 to 6, wherein said quenching is effected by dipping said seeds into water. The method of any of claims 1 to 8, which further comprises, after exposing said seeds to a temperature of about 70°C to about 90°C, subjecting said seeds to a chlorine treatment. A method of cultivating sprouted vegetables, which comprises: subjecting the seeds to a sterilizing treatment according to any of claims 1 to 9 and cultivating said sterilized seeds. The method of claim 10, wherein after said sterilizing treatment a second sterilization step is effected prior to said cultivating. The method of claims 10 or 11, wherein after the sterilizing and prior to cultivating, the seeds are soaked in water having a temperature of about 30° to 40°C.

Inventors: SUZUKI TOMOSABURO, TAKIZAWA TSUNEO, SUZUKI, TOMOSABURO, TAKIZAWA, TSUNEO
Applicants: DAISEY KIKAI CO LTD, DAISEY KIKAI CO., LTD.
Application year: 1994
Main classification: A61L2
IPC codes: A61L2, A01G9, A01C1